In 1959, the house was bought by the American School of Paris, which then settled there. In cleaning the building some Nazi materials were found.[citation needed] The story was that while the Germans occupied the building in World War II, the French Resistance was active in the tunnels of the old stone quarries under the building. These quarries had provided some of the stone used to build Paris. The school wanted to expand by putting up new buildings but the underlying tunnels made the ground unstable. A project was initiated to pump cement into the tunnels but this was abandoned, and the American School moved to another site in Saint Cloud.
https://en.wikipedia.org/wiki/Ch%C3%A2teau_de_Louveciennes